In the assembly of high density circuit boards, as well as other types of circuit-supporting substrate assemblages, various types of electrical components are often mounted on, and temporarily secured to, a circuit board, for example, before being soldered thereto through the use of thru-hole insertion-type terminals. As used herein, an electrical component is also understood to embrace any type of terminal-connected electrical device, such as a miniaturized relay. Similarly, all references to a circuit board hereinafter are understood to embrace a circuit-supporting substrate of any type, such as of ceramic material, which may form part of a circuit pack, for example.
It is often desirable that component insertable terminals be constructed and dimensioned such that force-fit, frictional contact is not established with thinly plated thru-hole sidewalls, for example. Any biting, or abrasive terminal-sidewall contact can often readily seriously damage, if not destroy, the conductive integrity of a given plated thru-hole.
Accordingly, when force-fit terminal insertion has not been desired heretofore, clinching of the ends of intentionally loosely inserted component terminals against the underside of a circuit board, for example, has normally been relied upon to provide temporary securement of board-mounted components prior to permanent soldered connections being established therebetween. It should be appreciated, however, that even clinched component terminals, particularly when the clinched ends are relatively short (as often dictated by circuit board space requirements), can often become dislodged from oversized thru-holes. This temporary securement problem is compounded whenever the terminal-secured components (or devices) have an appreciable mass, and/or a relatively high circuit board-mounted profile.
In addition, the prior use of conventional terminals of the so-called zero-insertion force type, in oversized thru-holes, has also often led to soldering defects. More specifically, when there is no terminal-thru-hole sidewall contact, generally referred to as a "bull's-eye", molten solder is often not satisfactorily drawn upwardly into the lower end of such a terminal-confining thru-hole by capillary attraction. When that happens, the resulting soldered connection may often prove to be defective either immediately, or after variable periods of use in the field. Unfortunately, such defective soldered connections many times are not readily detectable by visual inspection, even when magnified viewing is employed for that purpose.
Notwithstanding the problems encountered heretofore in using terminals formed with relatively smooth outer surfaces and undersized insertion sections (relative to a given sized thru-hole), so as to minimize otherwise possible damage to thinly plated thru-hole sidewalls, such terminals are normally considerably less expensive and easier to manufacture. Further, compared to terminals formed with barbed or sawtoothed edges, for example, terminals constructed for loose-fitting insertion are much easier to handle and manipulate during not only their fabrication, but subsequent securement to respectively associated electrodes of a component. Such terminals further significantly facilitate the magazine feeding, and subsequent insertion thereof in respectively aligned thru-holes of a circuit board, for example, particularly when automated equipment is employed for such processing operations.
Accordingly, there has been a definite need for a component terminal that is constructed in a manner that would not only facilitate the fabricating, electrode attaching, feeding and inserting operations relating thereto in a reliable and automated manner, but also facilitate the subsequent temporary securement thereof within an oversized thru-hole, as well as the attainment thereafter of a reliable permanent soldered connection therebetween.